Centrifugal-type pulp separator



CENTRIFUGAL-TYPE PULP SEPARATORv Filed Sept. 4, 1957 *ayz-in.

Patented Mar. 14, 1961 CENTRIFUGALTYPE PULP SEPARATOR Johannes Jung,Miltenberg (Main), Germany Filed Sept. 4, 1957, Ser. No. 682,050

'5 Claims. (Cl. 209-284) The present invention relates to acentrifugal-type pulp separator comprising a housing having a stationarycylindrically-shaped screen drum arranged at a certain distance from theinner wall of the housing, and blades inside the screen drum rotatingabout the drum axis, and in which the pulp enters from the one frontside and the coarse-grained parts leave the housing at the opposite end.

In known centrifugal-type separators of this kind the pulp enters thescreen drum in axial direction at a height of the shaft. In the drum thepulp is rotated by the blades. This necessitates a power input which isvery high as compared to the output of the screen drum. Furthermore, theimpacts on the rotating blades resulting from the axial flow of the pulpare of detrimental effect. Furthermore, when feeding the pulp in axialdirection at a height of the blade shaft, the screen is not uniformlycharged over its total length since the end facing the breast box is notcorrectly loaded.

To eliminate these disadvantages it has already been proposed to feedthe pulp at a height of the screen drum all over its periphery and tobend the ends of the blades which are inclined with respect to the axis,at the point of entry of the pulp so that a shockless entry of the pulpinto the impeller is achieved. At the point where sizing takes place,the blades are inclined so as to impart an axial movement to the pulp.By eliminating the impact of the entering pulp on the impeller, powerrequirements are reduced. As compared to the drum output, however, powerinput is still considerable since the axially supplied pulp has to becirculated. This reversal of movement takes place gradually, which againhas the disadvantage that the drum is less loaded at the point of entrythan in its center.

According to another known embodiment, power requirements are reduced inthat the screen drum which in conventional separators is stationary, isrotated at a speed somewhat lower than that of a Worm conveyor providedinstead of impeller blades. The rotating screen drum itself forms thecentrifugal member. The material is supplied at a height of the wormconveyor shaft to a double-walled hopper arranged concentric on thescreen drum, the hopper tapering towards the screen drums periphery. Inthis hopper the axially entering material is transferred, through meansof its friction on the wall and without causing any impact, into thedirection and speed of rotation of the screen drum. The material is thenspread as a uniform layer over all of the inner circumference of thescreen drum and smoothly passes over the separating area where the finefibers and the water are thrown out through the holes of the screen drumdue to its rotation. Efliciency is not as high as if the material isthrown against a stationary screen drum by rotating blades. A rotaryscreen drum considerably complicates the apparatus and increases itsmanufacturing cost.

It is, therefore, one object of the present invention, to provide ashockless entry of the pulp into the screen drum at a height of itsinner wall and all over its periphery, a utilization of the total lengthof screen, and a reduction of power requirements by arranging astationary feed pipe for the pulp which is shaped so that a rotarymovement is imparted to the pulp which follows the curvature of thescreen drum before the pulp enters the drum.

It is of particular advantage to supply the material fiom a breast boxthrough a double-walled pipe in which the space between the two wallsthrough which the material is passed, is provided with spiral channels,guide blades, or the like. These spiral passages impart a rotarymovement to the passing material. The spiral is shaped in such a mannerthat the direction of movement -of the material is the same as thedirection of rotation of the impeller blades. By controlling the feedfrom the breast box into the double-walled pipe, the amount of materialflowing into the pipe can be controlled, and by varying the level of thematerial in the breast box the feed pressure can be varied. If desired,one of the walls of the double-walled pipe may be of conical shape sothat the cross-section of passage gradually decreases towards theseparator. In these embodiments the front wall of the housing ispreferably shaped in such a manner that the pulp can enter the housingfrom the circumference of the feed pipe. Multiple spirals in the feedpipe take care of distributing the material over the entire inner edgeof the screen drum adjacent the feed pipe.

Similar to the feed of the pulp, the coarse-grained material remainingin the screen drum' may be discharged. For this purpose, the front sideof the housing opposite the feed pipe may be provided with anotherdouble-walled pipe through which the coarse-grained material is passedaway. When several separators are arranged in a row, the passed-awaycoarse-grained material can be directly supplied to the followingseparator. In this case, spirals have to be provided also in this pipewhich, however, can be disposed of when the coarse-grained material isfed directly from the separator to a refiner or to another station. Inthis embodiment the arrangement of several separators in a row, eachwith a finer mesh scren than the preceding one, is considerablysimplified. No special pipes and pumps for the transfer of the materialfrom one separator to the other are necessary. Furthermore, thedifferent separators may 'be successively mounted at the same level.

When for constructional reasons it-is not possible to mount a breastbox, the material is supplied to the pipe provided with the spiralpassages, through a feed channel or the like.

With these and other objects in View which will become apparent in thefollowing detailed description, the present invention will be clearlyunderstood in connection with the accompanying drawings, in which:

Figure l is an axial section of a centrifugal-type pulp separator havinga breast box disposed on the same plane and a double-Walled pipeconnecting both members, the space between the double walls serving forthe feeding of the material;

Fig. 2 is an axial section similar to that in Fig. 1, wherein, however,the space between the double walls is tapered down in direction towardsthe separator;-

Fig. 3 is an axial section of a centrifugal-type pulp separator having ahigher breast box and a doublewalled pipe connecting both members;

Fig. 4 is an end View of the separator shown in Fig. 3, indicating aspirally shaped pipe connecting the higher breast box with thecentrifugal type separator; and

Fig. 5 is an axial section of a plurality of separators disposed inseries and each of the separators being connected with the next one bymeans of a double-walled pipe and a higher breast box feeding thematerial to the first one of said separators. V

Referring now to the drawings and in particular to Fig. l, the separatorcomprises a cylindrical housing 1 having a screen drum 2 spaced apartfrom the inner wall of the housing. Impeller blades 3 are arrangedwithin the screen drum 2. Theshaft 9 carrying the impeller blades 3 isjournalled in the front and back sides of the housing 1.

Co-axial with the housing 1 is fixed a double-walled pipe 4 to the frontside of the housing, the space between the two walls of the pipe 4having spiral passages 5. The outer'diameter of the double-walled pipe 4corresponds with the diameter of the screen drum 2. The front side ofthe housing 1 to which the double-walled pipe 4 is fixed, is shaped insuch a manner that all of the periphery of the pipe 4 is incommunication with the inside of the screen drum 2.

The material to be separated is supplied from a breast box 6 through thedouble-walled pipe 4 to the separator. The material flowing through thespace between the two walls of the pipe 4 is put in circular motion bymeans of the spiral passages 5. The latter are shaped in such a mannerthat the circular motion corresponds with the direction of rotation ofthe impeller blades 3. The material fed to the separator through thepipe 4 reaches the inner Wall of the screen drum 2 at its entrance andspreads 'all over its circumference. To achieve perfect operation, thepipe 4 is provided with a multiple spiral. Since the material suppliedis already in a circular motion which corresponds with the direction ofrotation of the blades 3, the screen drum 2 is not subjected to greatstress when receiving the material. For the same reason it is notprobable that the blades 3 subject the material to an additional motion.

The speed at which the material flows through the V double-walled pipe 4corresponds with the pressure existing at the entry of the pipe 4 in thebreast box 6 and with the amount of material entering the pipe 4. Thepressure may be varied by varying the material level. in the breast box6, and the amount of material is controlled by a valve means 7 at theinlet of the pipe 4.

It is also possible to control the speed of the material supplied byvarying the pitch of the spiral in the doublewalled pipe 4. Preferably,the spiral is shaped in such a manner that its pitch is variable byexpanding or compressing the spiral.

By controlling' the speed of the material flowing through thedouble-walled pipe 4, it is easy to have the material enter theseparator at a speed corresponding with the circumferential speed of theimpeller blades 3. When these two speeds are synchronized, the stressacting on the screen drum is reduced to a minimum and the danger of thematerial being subjected to an additional movement is completelyeliminated. Thus, careful treatment of the material as well as gentleseparation is secured.

In the embodiment disclosed in Fig. 1 both walls of the pipe 4 are ofcylindrical shape. The cross-section of passage is uniform over thetotal length of the pipe 4. However, if for instance the material ishighly diluted, and a big output is to be rendered, it may be ofadvantage to have one wall of the double-walled pipe 4 tapered down, sothat the cross-section of passage is reduced towards the separator. Suchan embodiment is disclosed in Fig. 2.

The arrangement of the breast box 6 will depend on the available space.In the embodiments illustrated in Figs. 1 and 2 the breast box 6 isarranged at level with the separators, the material being supplied fromthe breast box 6 in axial direction, to the double-walled pipe 4.Asshown in a side and a front elevational view in Figs. 3 and the breastb X 6' may also be mounted above the double-walled pipe 4, and thematerial may be sup- "plied in radial direction from the box 6 to thedoublewalled pipe 4 through a spiral pipe .10.

When the coarse-grained material leaving the separator is to be furthertreated in another screen drum having a finer mesh screen, it isadvisable to arrange the outlet of the coarse-grained material at thefront side opposite the inlet and to shape it in such a manner that thecoarse-grained material is ejected over the entire circumference at aheight of the screen of the first separator. The coarse-grained materialleaving the separator here, is then passed into a double-walled pipehaving spirals inside and being fixed to the front side of theseparator, to transfer it into the second separator. In this way, anynumber of separators, each having a finer mesh screen, may be arrangedone after the other, as disclosed in Fig. 5. The coarse-grained materialis then passed from one separator to the other without the necessity ofemploying further pumps and pipes. It might be'necessary to feed waterto the pulp for further dilution between the various separators. Theseparators arranged in a row may be mounted at the same level and closeto each other. Space requirements are considerably reduced as comparedto the conventional arrangement of several separators working one afterthe other.

In some cases space conditions may not allow for an arrangement of abreast box with a transfer pipe to :the separator. In these cases a feedchannel or pipe leading to the double-walled pipe 4 may be providedinstead of a big-capacity box 6.

While I have disclosed several embodiments of the present invention, itis to be understood that these embodiments are given by example only andnot in a limiting sense, the scope of the present invention beingdetermined by the objects and the claims.

I claim:

1. .A centrifugal-type pulp separator comprising a housing having aninner wall, a stationary screen drum disposed in said housing spacedapart a predetermined distance from said inner wall and having its axisdisposed horizontally, a horizontal shaft axially disposed rotatably insaid housing, a plurality of impeller blades keyed to said shaft, a feedpipe disposed adjacent one end of said screen drum and feedingmaterialtangentially directly to the inner face of said screen drum inthe direction of rotation of said impeller blades, said screen drum inconjunction with said impeller blades operating as separating means forsaid pulp, said material emerging from said screen drum from theopposite end thereof, said feed pipe comprising two substantiallycontric pipe members, the outer diameter of said feed pipe correspondingwith the inner diameter of said screen drum and the inner diameter ofsaid feed pipe being slightly smaller than the outer diameter of saidimpeller blades, said feed pipe being disposed completely outside saidhousing and having a spiral intermediate wall extending over the entirelength of said feed pipe.

2. The separator, as set forth in claim 1 which includes a breast boxsupplying said material at a pressure and at an amount to said feedpipe, in order to impart the same rotary speed as said impeller bladesto said material when feeding the latter from said feed pipe to saidscreen drum.

3. The separator, as set forth in claim 1, wherein one of the walls ofsaid feed pipe is tapered, so that its crosssection of passage decreasesgradually towards the screen drum.

4. The separator, as set forth in claim 1, which includes a curved pipemounted to the front face of said feed pipe, said curved pipe beingadapted to feed said material to spiral passages, and a breast boxsupplying said material to said feed pipe by means of said curved pipeand being disposed at ahigher level than that of said screen drum.

5. A set of a plurality of separators, each of said :separators beingset forth in claim 1, wherein said separators are disposed .in series,so that said material is fed 6 from one of said separators to theadjacent one of said References Cited in the file of this patentseparators through said pipe, and the screen drum of UNITED STATESPATENTS each of said separators having, in the direction of movement ofsaid pulp through said plurality of separators, 1,583,705 Schmldt P 1923a finer mesh screen than the preceding one of said sep- 5 1,730,057 COX1930 arators. 1,356,176 Trimbey May 3, 1932

